Manual dispensing equipment is used in the development of model prototypes and performance machines for small batch pcb production or new products, as well as solder paste or mounting glue when repairing and replacing components in production.
1. Prepare solder paste
Install the copper solder paste, install the adapter connector, and twist and lock tightly and place it vertically on the syringe holder. According to the size of the pcb pad, plastic inverted needle tips of different inner diameters are selected.
2.Adjust the dispensing amount
Turn on the compressed air source and turn on the dispenser. Adjust the air pressure, adjust the time control knob, control the dispensing time, press the continuous dispensing method, press the switch, and the solder paste will continue to drip until the switch is released. Repeat the adjustment of the amount of solder paste. The amount of solder paste dripping is determined by the air pressure, the time of gas release, the viscosity of the solder paste, and the thickness of the tip. Therefore, the specific parameters should be set according to the specific conditions, and the parameters are mainly adjusted according to the amount of solder paste dropped on the PCB pad. After the solder paste drop amount is adjusted properly, it can be dispensed on the pcb.
3. Dispensing operation
Place the pcb flatly on the workbench and hold the needle tube so that the angle between the needle tip and the pcb is about 45°, and the dispensing operation is performed.
4. Common defects and solutions
Trailing is a common phenomenon in the dropping technics, where a thin line or "tail" is created at the top of the solder joint when the needle is removed. The tail may collapse and directly contaminate the pad, causing bridging connection, solder balls and virtual welding.
One of the reasons for the tailing is that the technics parameters of the dispenser equipment are not adjusted properly, such as the inner diameter of the needle is too small, the dispensing pressure is too high, the distance of the needle from the pcb is too large, etc. Another reason is not understand the performance of the solder paste completely, the solder paste is not compatible with the application technics, or the quality of the solder paste is not good, the viscosity changes or has expired. Other causes may also cause drawing/tailing, such as electrostatic discharge to the board, bending of the board, or insufficient support of the board. For the above reasons, the technics parameters can be adjusted, the needle can be replaced with a larger inner diameter , the pressure can be lowered, and the height of the needle from the PCB can be adjusted; testing whether the date, performance and using requirements of the solder paste used are suitable for the coating of the technics.